Department store chain John Lewis has said sales surged 36% in the week before Christmas, but it then saw a 9.4% slump between Christmas and new year as the timing of bank holidays skewed trading.
John Lewis said it rang up £175.6 million in sales over the week to December 24 as shoppers rushed to snap up last minute items online for entertaining, and as t wo extra days of trading this year boosted trade.
The following week was impacted by the fall of Christmas and new year, it added.
The Partnership's Waitrose supermarket business also saw the same trend, with sales soaring 31.1% to £109.7 million in the week to Christmas Eve, but pulling back sharply in the following week to December 31, down 12.5%.
Waitrose said more revellers chose to toast the new year with English sparkling wine as sales of the tipple jumped 65% against a 13% rise for champagne.
The employee-owned firm will report figures for the six weeks to December 31 next Thursday, when many of the major retailers will also reveal how they fared over Christmas.
It comes amid fears of a difficult festive season for the sector after Next kicked off with a dismal trading update, warning over annual profits after a worse-than-expected Christmas, while it said 2017 is set to be "even tougher".
John Lewis said eight of its top 10 selling items online were household products in the final Christmas trading week, with those hosting parties buying sets of china, white plates and cereal bowls.
Its website saw the busiest hour between 6pm and 7pm on Christmas Eve, following the launch of its clearance sale at 5pm, while shoppers hit the stores on December 27.
Best-sellers so far in online clearance sales include Mulberry handbags, Dyson vacuum cleaners and Samsung televisions, as well as beauty gift sets.
Entertaining and last-minute preparations also drove sales at Waitrose over the two-week period, with party food up 14%, Christmas cakes up 9% and frozen desserts increasing 11%.
Families looking for alternatives to the traditional turkey on Christmas Day helped sales of duck lift 13%, beef rise 6% and slow-cooked meats surge by 63%.